The lines in which \(J\) does not change are weaker (“satellite” lines), and the lines in which the change in \(J\) is in the opposite sense to the change in \(L\) are the weakest (“second satellites”...The lines in which \(J\) does not change are weaker (“satellite” lines), and the lines in which the change in \(J\) is in the opposite sense to the change in \(L\) are the weakest (“second satellites”). It was mentioned in Chapter 7 that one of the tests for \(LS\)-coupling was Hund’s interval rule, which governs the spacings of the levels within a term, and hence the wavelength spacings of the lines within a multiplet.
